This application claims the priority of Korean Patent Application No. 2003-41058, filed on Jun. 24, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an optical scanner using a curved mirror provided by a micro-electro mechanical system (MEMS) and a method of manufacturing the same, and more particularly, to an optical scanner for driving a stage with a curved mirror horizontally and for scanning light incident on the curved mirror in a wide angular range, and a method of manufacturing the same.
2. Description of the Related Art
FIG. 1 is a schematic perspective view of an optical scanner disclosed in U.S. patent application No. 2003-39089. Referring to FIG. 1, a rectangular frame 2 is formed on a substrate 1 which is formed of Pyrex glass, and a H-shaped stage 3 is positioned inside the frame 2 with a separating area therebetween. The stage 3 is suspended at a predetermined height from the substrate 1 by two supporters 4 which are positioned on a X axis. The stage 3 has a central area 31 that is directly connected to the supporters 4 crossing the separating area and four extended areas 32 that extend from the central area 31, parallel to the supporters 4 by a predetermined length. A mirror (not shown) may be formed only on the central area 31. Alternatively, the mirror may be formed on the entire surfaces of the central area 31 and the extended areas 32.
The supporters 4 have stationary support beams 42 extending from the frame 2 and torsion bars 41 that extend from the support beams 42 to the central area 31 of the stage 3, and the torsion bars 41 are deformed by the actuation of the stage 3. The torsion bars 41 are connected to a central portion of opposite sides of the central area 31 of the stage 3. The frame 2, the supporters 4, and the stage 3 form a single body. The torsion bars 41 support the seasaw motion of the stage 3 and provide a properly elastic restoring force during the actuation of the stage 3, and the frame 2 and the supporters 4 provide an electric path to the stage 3. The frame 2 includes a first partial frame 21 and a second partial frame 22 which are respectively positioned on and beneath a eutectic bonding layer 23 made of an AuSn alloy. The first partial frame 21, the stage 3, and the supporters 4 are obtained from one material substrate, e.g., one silicon wafer, through a multi-step process. Thus, the separating rectangular area exists between the first partial frame 21 and the stage 3, and the supporters 4 having the torsion bars 41 and the support beams 42 cross the separating area. Driving comb electrodes 33 are formed beneath the central area 31 and the extended areas 32 that extend from the central area 31. First fixed comb electrodes 13 are alternately disposed along with the driving comb electrodes 33 on the substrate 1 facing the central area 31 and the extended areas 32.
As shown in FIG. 1, second fixed comb electrodes 13′ are positioned beside the first fixed comb electrodes 13. The second fixed comb electrodes 13′ are an optional element, which is a kind of sensor for sensing the actuation of the stage 3 based on changes in electric capacitance. The first and second fixed comb electrodes 13 and 13′ are supported by bases 14 and 14′ positioned beneath the first and second fixed comb electrodes 13 and 13′. The base 14 and the first fixed comb electrodes 13 form a single body, and the base 14′ and the second fixed comb electrodes 13′ form another single body.
The above-described conventional optical scanner has a structure in which the stage 3 has the central area 31 and the extended areas 32 that extend from the central area 31 and the supporters 4 for supporting the stage 3 have the support beams 42 and the torsion bars 41 that are directly connected to the central area 31 of the stage 3. The optical scanner having the above structure performs optical scanning through the seasaw motion of a planar reflector formed on the stage. Since a restoring force generated by stiffness of a material of the structure is used as a main driving force, there is a limitation in a driving speed, a range in which driving comb electrodes move, that is, a scan range, is determined according to a seasaw angle of the stage, and the seasaw angle is limited when the stage and the substrate contact the fixed comb electrodes and driving comb electrodes, respectively.